Gamma cameras, in particular those which use so called pinholes, often have a (very) long scanning time, due to the relatively low sensitivity of the cameras. This may be unfavourable for the object to be examined, in particular a test animal or human being, since movements during the scanning time have to be prevented as much as possible. This may somewhat be ensured by anaesthetising or by simply not moving. In both cases, this is associated with discomfort for the test animal or human being. Furthermore, in the prior art it is rather common to first position the object to be examined roughly before the gamma camera, in particular if a gamma camera with a small scanning volume is used. After that, a gamma image is formed, on the basis of which it is determined where the scanning volume is located within the object to be examined. Subsequently, the required adjustment in the positioning is carried out. Often, gamma cameras with a high resolution have a small focusing volume, as a result of which “navigating” the focus volume is difficult. This increases the scanning time unnecessarily. In this application, “examining” means collecting data on the object, or part thereof, by means of the gamma camera.
From the article “Detecting Patient Motion in SPECT Imaging Using Stereo Optical Cameras” by Gennert et al., a system is known wherein an image of e.g. a patient is made with gamma cameras, and wherein, at the same time, webcameras make an optical image of the patient. The optical images are used to follow the movement of the patient and to calibrate the images of the gamma camera.
The known system however has the disadvantage that it may not always be used, or at least not well, with many gamma detection systems. This is in particular the case for gamma detection systems with a high resolution that use pinholes positioned close to the object to be examined, and the like. For example, this relates to gamma detection devices in which a test animal is positioned in a narrow tube. In such a case in particular, there is little space for the optical cameras, for these can not be placed in the field of view of the gamma cameras. Also, a good lighting of the object is very difficult in such case.